<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <button @click="add">+</button>
        <span>{{num}}</span>
        <button @click="sub">-</button>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>

    <script>
        var app = new Vue({
            el: "#app",
            data: {
                message: "hhhh",
                num:1
            },
            methods: {
                add:function(){
                    // console.log(this.num++);
                    if(this.num<10){
                        this.num++;
                    }else{
                        alert("别点了，最大了")
                    }
                },
                sub:function(){
                    // console.log(this.num--);
                    if(this.num>0){
                        this.num--;
                    }else{
                        alert("别点了，最小了")
                    }

                }
            }
        })
    </script>
</body>

</html>